Sound transforming and reproducing apparatus



April 7, 1931. a; WURDEL ET AL 1,799,942

SOUND TRANSFORMING AND REPRODUCING APPARATUS Filed Sept. 5, 1928 2 Sheets-Sheet 1 Fig.2

if Ewe/2107's G'nt/Ler ZQraleZ t2 ,5; $2961 A ril 7, 1931. G. WURDEL ET AL SOUND TRANSFORMING AND REPRODUCING APPARATUS Filed Sept. 5, 1928 2 Sheets-Sheet 2 f" 5 Patented Apr. 7, 1931 UNITED STATES PATENT OFFICE GCTNTHER WUB-DEL AND FRITZ SPIEGEL, OF BERLIN, GERMANY, ASSIGNORS TO WALTER VOLLMANN, OF BERLIN, GERMANY v SOUND TRANSFORMING AND REPRODUCING APPARATUS Application filed September 5, 1928, Serial No. 304,000, and in Germany May 5, 1928.

Our invention relates to improvements in sound transforming and reproducing apparatus, and more particularly in the construction of the diaphragm. The object of the improvements is to provide an apparatus in which the diaphragm operating member has as far as possible a uniform action over the entire surface of the dianhragm, so that the efiiciency of the diaphragm in transforming or reproducing sounds is high. lVith this object in view our invention consists in constructing the diaphragm of a plurality of sections fixed to a frame or sound box or the like and having independent movement, the said sections being separated from each other at their adjacent edges by narrow gaps, and the inner ends of the sections being joined to form a rigid whole. The width of the said gaps is so small that in the operaiton of the diaphragm the air does not practically pass through the same, and in. some cases we provide non-elastic or flexible members for covering the said gaps.

Another object of the improvements is to provide a diaphragm which is adapted to various tone frequencies, and with this object in view the diaphragm is composed of sections having different elasticities. Other objects of the improvements will appear from the following description.

For the purpose of explaining the invention several examples embodying the same have been shown in the accompanying drawings in which the same reference characters have been used in all the views to indicate corresponding parts. In said drawings,

Fig. 1, is a sectional elevation showing a sound box of a loud speaker,

Figs. 2 and 3, are respectively a front elevation and a rear elevation of Fig. 1,

Fig. 4, is a perspective view of the inner end of the diaphragm,

Fig. 5, is a rear elevation of the sound box of a loud speaker showing a modification,

Fig. 6. is a perspective view of the inner end of the diaphragm shown in Fig. 5,

Fig. 7, is a detail sectional elevation illustrating another modification,

gis a ss-section taken on th line 8--8 of Fig. 7

Fig. 9, is a front elevation showing another modification of the sound box of the loud speaker, and

Fig. 10 is a cross section of the modification shown in Fig. 9.

In most of its features our invention may be embodied in sound transforming apparatus such as microphones as well as in sound reproducing apparatus. In the following description we shall describe the same as embodied in the sound box of loud speakers. The invention is particularly adapted to large area reproducing apparatus, that is, to loud speakers and other devices which de pend on the diaphragm for the full reproduction of sound and do. not require the use a born to increase the volume of the sound. It is also adapted for diaphragms which are freely radiating, as defined below.

In the loud speaker represented in Figs. 1-4:, the diaphragm consists of four sectors 1, which are bent inwardly in the manner shown in Fig. 1. The outer edge 2 of each of the parts 1 forms a plane surface, and the curvature gradually increases towards the centre of the diaphragm. The edges 2 of the parts 1 are clamped in a casing 3, for example of wood, by being held between fillets 5 and interposed flexible members 4. The parts 1 are cut in such a way that, when placed in juxtaposition, their curved adjacent edges 6 do not come into mutual contact, narrow gaps 7 being left between said edges.

The ends 8 of the parts 1 are folded in the direction of the axis of the diaphragm, so as to produce a stiffening effect, as shown in Fig. 4:. The folded ends are relatively disposed, so as to form a cross having four ribs 9, adjoining the gaps 7, the ends 8 being combined to form a rigid unit. The reed 10 of the armature, which is actuated with the tempo of the talking currents, engages at the point of intersection of the ribs 9. In this embodiment. the armature and magnet are housed in the box 12, which may be of any type.

During the reciprocal oscillation of the diaphragm composed of the four sectors 1, the curvature of the parts 1 decreases and a disturbing effect on the oscillations and might even causefluttering of the dia phragmis practically precluded by malting the gaps 7 as narrow as possible. At the same'time, even very small oscillations are well transmitted so that the tone is comparatively loud, even with a low'ene'rgy of reception, because the ends 8 ofthe parts 1 are combined to a rigid unit which is acted upon by the reed 10 of the-armature. The

oscillations are therefore propagated in a uniform manner from the rigid ends 8, 9'to the several parts 1 of the diaphragm and thus over the entire surface of same.

In theembodim'e'nt according'to Figs. 5

and 6, the gaps 7 are covered over, on the rear side of the diaphragm by strips 13 of some flexible material, such as leather, which, for example, are attached to the paper parts 1 by gluing. The cover strips 13 prevent any of the agitated air from penetrating to the rear side of the diaphragm, so that any disturbances which might be caused by such penetration are entirely prevented. Nevertheless, the flexibility of the cover strips 35 "'leaves the sectors 1 sucha degree of mobility that their radial edges 6 arefree to move in accordance with the change in the curvature.

The manufacture of the diaphragm can be facilitated by making the rigid end separate, instead of from the diaphragm itself, and then attaching it to the ends 8. In the em bodiment according to Fig. 6, the rigid end consists of a separately made rigid cone 14, "-to the-perimeter of which the ends 8 of the diaphragm members'l are secured, for example'with glue. If, in so doing, the ends 8 be adapted to it the shapeof the cone, they will also be stiffened, by this curvature, in such a: way that the oscillations are uniformly transmitted from the rigid end 14 to the-diaphragm members 1.

When certain materials, such as pertinax, are employed for the membrane, it is inadvisable to secure the ends 8 of the diaphragm members 1*to'the separately made rigid end by gluing, pertinairbeing difficult to glue on. For this'reasom'in the embodiment accor-ding to-Fig; 7 two clamping cones lo and '16are provided," which fit one'in the other and are traversed by an axial screw 17. At the end projecting from the outer cone 15, this screw is attached to the armature of the magnet mechanism, housed in the box 12,

whilst the otherend, situated inside themner cone 16 is provided with a nut 18, thereby enabling the two clamping cones 15 and 16 to be tightened up.

The ends 8 of the four sectors 1 of the diaphragm (Fig. 8) are inserted between the two clamping cones 15 and 16, and are gripped tightly bet con the two cones by tightening up the screw 17. in this manner, the ends are bent in conformity with the curvz'itureof the surface of the cones 15 and 16, the ends being stiffened to a degree which gradually diminishes towards the clamped outer margins of the diaphragm members 1. ln tl is way, the ends 8 are comained into a rigid unit without having to be glued.

The rigid ends of the diaphragm may, of course, also be made of pyramidal sha 3e, and in place of four sect rs, the diaphragm may be composed of only three, or of a larger number than four, sectors.

it is known that, according to its thickness, he elasticity of its material and its'superficial area, each diaphragm displays a preference for certain tone frequencies whilst the higher and lower ranges of frequency are;

neglected. so that the tone reproduction is unnatural. The diaphragm constructed f aluralit of sector'members can be designed so as to reproduce all tone frequencies in a uniform manner.

For this purpose, the sector members 1 of the diaphragm are made of different thicknesses, as shown in Fig. 10, the thinner members then favouring the higher frequencies,

and the thicker members the lower frequencies. The same result is obtained when'the several diaphragm members differ in the elasticity of their material, certain members consisting, for example, of pertinax, and the others of drawing paper.

With the same object, the members 1 of the diaphragm may be of different superficial area. F 1g. 9 shows an embodiment of the loud speaker in which the rigid unit-formed by combining the ends o the diaphragm mem;

hers is disposed'eccentrically in the rectangular casing 3. In this manner, 1n theembodiment shown, there result four diaphragm members, two of wh ch, 19, are 'of equal'area, the member 20 having a larger area, and the member 21 a smaller area. The smallest member 21 favours relatively high tone freemitted can move freely without' any interspeakers ference caused by the presence of walls or other obstructions. In other words, the diaphragm is freely radiating and this is the meaning of these words in the claims.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be per formed, we declare that what We claim is:

1. tloand transforming and reproducing apparatmi, comprising a box, and a diaphragm of large area mounted on said box and composed of a plurality of sections having independent movement, said sections being separated from each other at their adjacent margins and connected with each other at their median parts, and flexible members covering the gaps provided between the adj acent edges of said sections.

2. Sound transforming and reproducing apparatus, comprising a box, and a dia phragm of large area mounted on said box and composed of a plurality of sections curved from their outer margins inwardly and having independent movement, said sections being separated from each other at their adacent margins and connected with each other at their median parts, and flexible members covering the gaps provided between the ad j acent edges of said sections.

3. Sound transforming and reproducing apparatus, comprising a box, and a diaphragm mounted on said box and composed of a plurality of sections curved from their outer margins inwardly and having independent movement, said sections being bent into angular form at their inner adjacent ends to form ribs, and said inner ends being connected with one another, and means for connecting the diaphragm operating member to said inner ends.

4. Sound transforming and reproducing apparatus, comprising a box, and a diaphragm mounted on said. box and composed of a plurality of sections having different superficial areas and having independent movement, the inner adjacent ends of said sections being disposed eccentrically of said frame or box.

5. A diaphragm of large area for loud for setting up sound waves comprising at least three substantially triangular membranes rigidly secured along one edge, and laterally curved therefrom to their apices, said apices being secured. together and adapted to be acted upon by a vibratory member, the free edges of said membranes being adj acent to but spaced from each other to allow free individual movement of the membranes.

6. A diaphragm for loud speakers for setting up sound waves comprising at least three substantially triangular membranes rigidly secured along one edge, and laterally curved therefrom to their apices, said apices being secured together and adapted to be acted upon by a vibratory member, the free edges of said membranes being adjacent to but spaced from each other to allow free individual movement of the membranes, said diaphragm being freely radiating.

7. A diaphragm for loud speakers for setting up sound waves comprising at least three substantially triangular membranes rigidly secured along one edge, and laterally curved therefrom to their apices, said apices being scoured together and adap ed to be acted upon by a vibratory member, the free edges of said membranes being adjacent to but ipaced from each other to allow free individual movement of the membranes, and said membranes being of different elasticity.

8. A diaphragm for loud speakers for setting up sound waves comprising at least three substantially triangular membranes rigidly secured along one edge, and laterally curved therefrom to their apices, said apices being secured together and adapted to be acted upon by a vibratory member, the free edges of said membranes being adjacent to but spaced from each other to allow free individual movement of the membranes, said diaphragm being freely radiating, and said membranes being of different thic mess.

9. A diaphragm for loud speakers for setting up sound waves comprising at least three substantially triangular membranes rigidly secured along one edge, and laterally curved therefrom to their apices, said apices being secured together and adapted to be acted upon by a vibratory member, the free edges of said membranes being adjacent to but spaced from each other to allow free individual movement of the membranes, said diaphragm being freely radiating, and said membranes being of different superficial areas.

10. A loud s eaker comprising a box having an open side, a diaphragm of large area closing said side, said diaphragm comprising a plurality of substantially triangular membranes, the outer edges of said membranes being rigidly secured to the box, the apices of said membranes being secured together, and the free edges of the membranes being adj acent to but spaced from each other to allow free individual vibration, and means in said box for imparting vibratory movement to said membranes.

11. A loud speaker comprising a box having an open side, a diaphragm closing said side, said diaphragm comprising a plurality of substantally triangular membranes, the outer edges of said membranes being rigidly secured to the box, the apices of said membranes being secured together, and the free edges of the membranes being adjacent to but spaced from each other to allow free individual vibration, and means in said box; for imparting vibratory movement to said membranes, said diaphragm being freely radiating.

12. A loud speaker comprising a box havingan open side, a diaphragm of large area closing said side, said diaphragm comprising a plurality of substantially triangular membranes, the outer edges of said membranes being ri idly secured to the box, the apices of said membranes being secured together, and the free ed es of the membranes b6111 adb b 3acent' to but spaced from each other to allow free individual Vibration and means in "said box for imparting vibratory movemei'it to saidmembranes, and flexible members covering the gaps between the adjacent edges of said membranes. I

In testimony whereof We hereunto afiix our signatures.

GUNTHER WURDEL. FRITZ SPIEGEL. 

